Erik Kostson
Ansys Employee

So just use as before - the sample example I showed is modeling an impedance tube with a sample in it, so just as you show.

The test sample is either JCA or Delany-Bazley, and that is it.

have in mind that we only need/have acoustic elements so the degree of freedom is only pressure so no need for displacements.
For rigid wall in acoustics:
Where ever we do not prescribe boundary conditions on the acoustic outer domain (so all outer faces) they will be acoustically hard (so acoustic velocity is zero there), so these are natural boundary conditions.
(If you still want to do it and define them, which we do not have to as I said above, there is an acoustic boundary condition called rigid wall).
So that rigid body in the back does not have to be modelled since it just provides a rigid wall at the back of the sample which we have if we do not assign any boundary conditions there as mentioned above, or if we assign a rigid wall at the back of the sample.

Thank you